Double-sided, polygonal cutting inserts with alternating concave and convex cutting edged

ABSTRACT

A double-sided, polygonal cutting insert includes a first surface and a second surface opposite the first surface. A plurality of side surfaces extend between the first surface and the second surface. A plurality of primary concave cutting edges are formed at an intersection between the plurality of side surfaces and the first and second surfaces, and a plurality of convex wiper edges are formed at an intersection between the plurality of side surfaces and the first and second surfaces. Each wiper edge has a step extending radially outward from a respective side surface. The cutting insert is mounted in a cutting tool such that the primary cutting edge and a wiper edge contact a workpiece to produce a high-quality surface finish on the workpiece.

RELATED APPLICATION DATA

The present application claims priority pursuant to 35 U.S.C. § 119(a)to Indian Patent Application Number 201941026958 filed Jul. 5, 2019which is incorporated herein by reference in its entirety.

FIELD

The invention pertains to the field of indexable cutting inserts. Moreparticularly, the invention pertains to an indexable, double sided,polygonal cutting insert with alternating concave and convex cuttingedges.

BACKGROUND

Modern high-performance cutting tools use replaceable and typicallyindexable inserts owing to the high cutting speeds and feeds supportedby the superior insert materials. Common materials for inserts includetungsten carbide, polycrystalline diamond and cubic boron nitride.

Indexable inserts use a symmetrical polygonal shape, such that when thefirst cutting edge is blunt they can be rotated or flipped over,presenting a fresh cutting edge which is accurately located at the samegeometrical position. Geometrical repeatability saves time inmanufacturing by allowing periodical cutting edge renewal without theneed for tool grinding, setup changes, or entering of new values into aCNC program.

Common shapes of indexable inserts include square, triangular andrhombus (diamond) providing four, three and two cutting edges,respectively, on each side of the insert. A double-sided or invertiblesquare insert, for example, can be flipped over to provide eight cuttingedges.

The number of cutting edges is directly related to the cost per edge ofthe cutting insert. The more cutting edges that are available, the morethe cutting insert has value. Thus, it is desirable to provide a cuttinginsert with multiple cutting edges. In addition, it is desirable for acutting insert that provide a high-quality surface finish.

SUMMARY

The problem of reducing the cost of the cutting insert and providing ahigh-quality surface finish is solved by providing a double-sided,indexable, polygonal cutting insert that has alternating concave andconvex cutting edges. All the concave and convex cutting edges can beused in a single right hand style milling cutter, which provides a truecutting and wiper insert.

An aspect of the present invention is to provide a double-sided,polygonal cutting insert, comprising a first surface, a second surfaceopposite the first surface, a plurality of side surfaces extendingbetween the first surface and the second surface, each side surface isperpendicular to the first surface and the second surface, a pluralityof primary cutting edges formed at an intersection between the pluralityof side surfaces and the first surface, a plurality of wiper edgesformed at an intersection between the plurality of side surfaces and thefirst surface, each wiper edge having a step extending radially outwardfrom a respective side surface and formed with a substantially planarouter surface.

Another aspect of the present invention is to provide a double-sided,polygonal cutting insert, comprising a first surface, a second surfaceopposite the first surface, a plurality of side surfaces extendingbetween the first surface and the second surface, a plurality of primarycutting edges formed at an intersection between the plurality of sidesurfaces and the first surface and a plurality of primary cutting edgesformed at an intersection between the plurality of side surfaces and thesecond surface, a plurality of wiper edges formed at an intersectionbetween the plurality of side surfaces and the first surface and aplurality of wiper edges formed at an intersection between the pluralityof side surfaces and the second surface, each wiper edge having a stepextending radially outward from a respective side surface and formedwith a substantially planar outer surface.

A further aspect of the present invention is to provide a cutting toolcomprising a tool body having a plurality of pockets for mounting acutting insert, wherein at least one primary cutting edge of a firstcutting insert mounted in a first pocket and at least one wiper edge ofa second cutting insert mounted in a second pocket contact a workpieceduring a cutting operation, thereby producing a high-quality surfacefinish on the workpiece.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an isometric view of a first surface of a cutting insert inaccordance with another embodiment of the invention.

FIG. 2 is a top view of the cutting insert of FIG. 1.

FIG. 3 is a side view of the cutting insert of FIG. 1.

FIG. 4 is a front view of a cutting tool, such as a milling cutter, withthe cutting insert of FIG. 1 mounted in a pocket of the cutting tool.

DETAILED DESCRIPTION

FIGS. 1-4 illustrate a cutting insert 10 in accordance with anembodiment of the present invention. The cutting insert 10 may comprisea double-sided, polygonal cutting insert. In the embodiment shown, thecutting insert 10 is of a generally octagonal shape that is symmetricabout a central axis 24 and includes four primary cutting edges and fourwiper edges on each side for a total of eight primary cutting edges andeight wiper edges. However, it will be appreciated that the inventioncan be practiced with any suitable shape and any multiple number ofprimary cutting edges and wiper edges, so long as the number of primarycutting edges is approximately equal to the number of wiper edges.

As shown in FIGS. 1-3, the cutting insert 10 includes a first surface12, a second surface 14 on an opposite side with respect to the firstsurface 12 and a plurality of side surfaces 16 extending between thefirst surface 12 and the second surface 14. Because the cutting insert10 is symmetric about all three axes (x-, y-, z-), only the firstsurface 12 will be described in detail herein for brevity. However, itwill be appreciated that any discussion of the first surface 12 appliesto the second surface 14.

In the embodiment shown, each side surface 16 is substantiallyperpendicular to both the first and second surfaces 12, 14. In otherwords, the first and second surfaces 12, 14 are substantially parallelto each other and perpendicular to the side surfaces 16. That is, theside surfaces 16 have a facet clearance angle of zero degrees. Thus,both the first and second surfaces 12, 14 of the cutting insert 10 canbe presented to the workpiece. In the embodiment shown, the cuttinginsert 10 has a total of eight side surfaces 16. Each side surface 16 isidentical to each other. Thus, only one side surface 16 will bedescribed herein for brevity, and it will be appreciated that anydescription herein of one of the side surfaces 16 applies to all theside surfaces 16.

A primary cutting edge 18 is formed at the intersection between thefirst surface 12 and a respective side surface 16 for a total of fourprimary cutting edges 18. In addition, a primary cutting edge 18 isformed at the intersection between the second surface 14 and arespective side surface 16 for a total of four additional primarycutting edges 18 (i.e. a total of eight primary cutting edges 18 for thecutting insert 10). Each cutting edge 18 is identical to each other.Thus, only one cutting edge 18 will be described herein for brevity, andit will be appreciated that any description herein of one primarycutting edge 18 applies to all the primary cutting edges 18.

Similarly, a wiper edge 19 is formed at the intersection between thefirst surface 12 and a respective side surface 16 for a total of fourwiper edges 19. In addition, a wiper edge 19 is formed at theintersection between the second surface 14 and a respective side surface16 for a total of four additional wiper edges 19 (i.e. a total of eightwiper edges 19 for the cutting insert 10). Each cutting edge 19 isidentical to each other. Thus, only one cutting edge 19 will bedescribed herein for brevity, and it will be appreciated that anydescription herein of one wiper edge 19 applies to all the wiper edges19.

As shown in FIGS. 3 and 4, each primary cutting edge 18 may be formed asa concave edge along the central longitudinal axis 24 and each wiperedge 19 may be formed as a convex edge central longitudinal axis 24. Inaccordance with an embodiment of the present invention, the centralportion of each primary cutting edge 18 may be lower in elevation thanthe outer portions of the primary cutting edge 18 adjacent to the cornerradiuses 20. The primary cutting edge 18 may be formed with a radius,R_(C), as shown in FIG. 3. For example, the radius R_(C) may typicallyrange from about 10 to about 100 mm, or from about 15 to about 70 mmdepending on the application and the capability of the milling cutter.In a particular embodiment, the radius R_(C) is about 23.7 mm (0.933inch). In accordance with an embodiment of the present invention, thecentral portion of each wiper edge 19 may be higher in elevation thanthe outer portions of the wiper edge 19 adjacent to the corner radiuses20. The convex wiper edge 19 may be formed with a radius, R_(W), asshown in FIG. 3. For example, the radius R_(W) may typically range fromabout 10 to about 100 mm, or from about 20 to about 60 mm depending onthe application and the capability of the milling cutter. In aparticular embodiment, the radius R_(W) is about 36.4 mm (1.433 inches).

As can be seen in FIGS. 1-4, each primary cutting edge 18 is separatedby a wiper edge 19. That is, the primary cutting edges 18 and the wiperedges 19 are arranged in an alternating fashion on the same side of thecutting insert 10. In accordance with an embodiment of the presentinvention, the alternating primary cutting edges 18 and wiper edges 19form a compound curve between each primary cutting edge 18 and eachadjacent wiper edge 19. In addition, the intersection of the firstsurface 12 and a respective side surface 16 that forms the primarycutting edge 18 also forms the wiper edge 19 at the intersection of thesecond surface 14 and the same respective side surface 16. Thus, theprimary cutting edges 18 and the wiper edges 19 alternate between thefirst surface 12 and the second surface 14.

Because the cutting insert 10 has an even number of sides 16, there arean identical number of primary cutting edges 18 and wiper edges 19.However, it should be appreciated that the primary cutting edges 18 andthe wiper edges 19 can be arranged in a non-alternating fashion.

A corner radius 20 connects each side surface 16 and extends between thefirst surface 12 and the second surface 14. In certain embodiments, eachcorner radius 20 has a radius in the range between approximately 0.5 mmto approximately 3.0 mm. For example, the corner radius 20 may have aradius of about 2.0 mm (0.08 inches). Because each corner radius 20 issubstantially identical to each other, only one corner radius 20 isdiscussed herein for brevity, and it will be appreciated that anydescription herein of one corner radius 20 applies to all cornerradiuses 20. In accordance with an embodiment of the present invention,the plurality of corner radiuses 20 extend between each of the pluralityof primary cutting edges 18 and each of the plurality of wiper edges 19.

The cutting insert 10 also includes a countersunk bore 22 extendingthrough the first and second surfaces 12, 14, and a central longitudinalaxis 24. It should be appreciated that the cutting insert is mirrorsymmetric about all three axes (x-, y- and z-axes). As a result, thecutting insert 10 comprises a double-sided cutting insert in which allsixteen cutting edges 18, 19 at the intersection between the sidesurfaces 16 and each of the first and second surfaces 12, 14 canseparately be used in a machining operation.

The first surface 12 (and the second surface 14) has a topographyincluding a substantially planar central region 26 surrounding thecountersunk bore 22. The central region 26 extends from the countersunkbore 22 and terminates in an irregular-shaped boundary 28. The firstsurface 12 also includes a rake face 30 extending radially inward fromeach cutting edge 18. In accordance with an embodiment of the presentinvention, each rake face 30 has a concave topography and is lower inelevation than the central region 26. The rake faces 30 associated withthe wiper edges 19 may include unique indicia to identify the wiper edge19. Alternatively, the rake faces 30 associated with the primary cuttingedges 18 may include the unique indicia, or both the primary cuttingedges 18 and the wiper edges 19 may include the unique indicia.

Each primary cutting edge 18 and each wiper edge 19 has a cutting-edgelength, CL, given by:

$\begin{matrix}{{CL} = {{{IC}\; {\tan \;\left\lbrack \frac{180{^\circ}}{\# \; {CE}} \right\rbrack}} - {CR}}} & (1)\end{matrix}$

where, IC is the diameter of an inscribed circle of the cutting insert10; #CE is the number of cutting edges 18, 19 (i.e. equal to 8); and CRis the magnitude of the corner radius 20. For example, for a cornerradius equal to 2.0 mm, CR is equal to 2.0.

Thus, for the octagon cutting insert 10 of the illustrated embodiment,the #CE is equal to 8. Thus, each cutting edge 18, 19 of the cuttinginsert 10 has a cutting-edge length, CL, given by:

CL=IC tan(22.5)−CR  (2)

An inscribed circle is the largest possible circle that can be drawninside the cutting insert 10. It should be appreciated that for apolygon, a circle is not actually inscribed unless each side 16 of thecutting insert 10 is tangent to the circle. For a regular polygon, suchas the cutting insert 10, an inscribed circle touches the midpoint ofeach side 16. By contrast, a circumscribed circle touches the cornerradius 20 between each side 16 of the cutting insert 10. As will beappreciated, the diameter of the inscribed circle is a function of thesize of the cutting insert 10. The larger the cutting insert 10, thelarger the diameter of the inscribed circle that can be drawn to toucheach of the cutting edges 18.

As shown in FIG. 2, the inscribed circle related to the primary cuttingedges 18 has a first diameter, D1, and the inscribed circle related tothe wiper edges 19 has a second diameter, D2, which is slightly largerthan the first diameter, D1. In one embodiment, the first diameter, D1,is approximately 20.0 mm (0.787 inches) and the second diameter, D2, isapproximately 20.2 mm (0.795 inches). The larger, second diameter, D2,is a result of the wiper edges 19 being formed with a step 34 protrudingradially outward from the side surface 16. The step 34 is formed with asubstantially planar outer face 36.

In accordance with an embodiment of the present invention, the outerface 36 of the step 34 is flat along the length of the wiper edge 19.For example, the substantially planar outer face 36 may extendsubstantially straight from a first corner radius 20 to a second cornerradius 20. In certain embodiments, the substantially planar outer face36 may be perpendicular to the first and second surfaces 12, 14.Alternatively, the substantially planar outer face 36 may be at anoffset angle with respect to the first and second surfaces 12, 14. Thesubstantially planar outer face 36 may be provided at an angle withrespect to the side surface 16. Each step 34 has a height along the sidesurface 16 selected to allow the cutting insert 10 to be mounted in acutting tool. For example, the height of the step 34 may be less than 30percent of the height of the side surface 16, for example, the height ofthe step 35 may be from 5 to 25 percent, or from 10 to 20 percent of theheight of the side surface 16. In accordance with an embodiment of thepresent invention, the step 34 comprises a top surface that intersectswith the planar outer face 36 to form the wiper edge 19. As shown inFIGS. 3 and 4, the top surface of the step 34 may be convex along thecentral longitudinal axis 24 of the cutting insert 10. In certainembodiments, a central portion of the top surface of the step 34 of thewiper edge 19 may be higher in elevation than the adjacent cornerportions 20.

Referring now to FIG. 4, a cutting tool 100, for example, a millingcutter, is shown according to an embodiment of the invention. Themilling cutter 100 comprises a tool body 112 including a cutting end 114with a plurality of circumferentially-spaced pockets 116, and a mountingend 118 opposite the cutting end 114. The tool body 112 is designed tobe rotatably driven about a central longitudinal axis 113A. In theillustrated embodiment, the milling cutter 100 is commonly known as aright-hand milling cutter and includes a total of six pockets 116.However, it will be appreciated that the invention is not limited by thenumber of pockets 116, and that the invention can be practiced with anydesirable number of pockets that provide the desired cuttingcapabilities. Each of the pockets 116 can receive a cutting insert,which is securely held in the pocket 116 by means of a mounting screw119. However, any other suitable method of securing the cutting insertin the pocket may be used, e.g., a clamping wedge, bolts, pins, or thelike. In the embodiment shown, the pockets 116 of the cutting tool 100receive a plurality of conventional cutting inserts 5 and a singlecutting insert 10. However, any other suitable arrangement may be used,e.g., two, three, four, five, six or more cutting inserts 10 may bereceived in the pockets 116 of the cutting tool 100.

The side surfaces 16 of the cutting insert 10 engage the pocket 116 whenthe cutting insert 10 is mounted in the tool body 112 during cuttingoperations. In certain embodiments, one of the first and second surfaces12, 14 and at least two side surfaces 16 should engage the tool body 112when the cutting insert 10 is properly indexed in the tool body 112. Itwill be appreciated that each of the cutting edges 18, 19 can be indexedinto an active position and effectively utilized in the milling cutter100, as shown in FIG. 4. It will be appreciated that the number ofcutting edges 18, 19 and the number of times that the cutting insert 10can be indexed depends on the geometric shape of the cutting insert 10.In general, the number of times the cutting insert 10 of the inventioncan be indexed is equal to the total number of pairs of primary cuttingedges 18 and adjacent wiper edges 19. As shown in FIGS. 1-4, the cuttinginsert 10 can be indexed eight times, unlike conventional rectangular orsquare cutting inserts with fewer number of cutting edges.

In accordance with an embodiment of the present invention, a singlecutting insert 10 can be mounted in a pocket 116 of the milling cutter100 such that a wiper edge 19 contacts the workpiece. In certainembodiments, the cutting edges of the conventional inserts 5 and thecutting edge 18 of the cutting insert 10 produce a rough cut of theworkpiece, while the wiper edge 19 produces a high-quality surfacefinish on the workpiece. For example, in a milling cutter with a totalof six pockets 116, five conventional cutting inserts 5 can be mountedin a respective pocket 116 such that the cutting edge contacts theworkpiece, and the cutting insert 10 can be mounted in a respectivepocket 116 such that the wiper edge 19 contacts the workpiece, therebyproducing a high-quality surface finish on the workpiece. During acutting operation, at least one primary cutting edge 18 and at least onewiper edge 19 of the cutting insert 10 may be in contact with theworkpiece. In certain embodiments, the cutting edges of the conventionalinserts 5 may be similar to the cutting edges 18 of the cutting insert10. In accordance with an embodiment of the present invention, the wiperedge 19 of the cutting insert 10 protrudes axially away from the toolbody 112 compared to the cutting edges of the conventional cuttinginserts 5. In accordance with an embodiment of the present invention,the wiper edge 19 of the cutting insert 10 may protrude axially awayfrom the tool body 112 compared to the cutting edge 18 of the cuttinginsert 10.

The patents and publications referred to herein are hereby incorporatedby reference.

For purposes of the description above, it is to be understood that theinvention may assume various alternative variations and step sequencesexcept where expressly specified to the contrary. Moreover, other thanin any operating examples, or where otherwise indicated, all numbersexpressing, for example, quantities of ingredients used in thespecification and claims, are to be understood as being modified in allinstances by the term “about”. Accordingly, unless indicated to thecontrary, the numerical parameters set forth are approximations that mayvary depending upon the desired properties to be obtained by the presentinvention. At the very least, and not as an attempt to limit theapplication of the doctrine of equivalents, each numerical parametershould at least be construed in light of the number of reportedsignificant digits and by applying ordinary rounding techniques.

It should be understood that any numerical range recited herein isintended to include all sub-ranges subsumed therein. For example, arange of “1 to 10” is intended to include all sub-ranges between (andincluding) the recited minimum value of 1 and the recited maximum valueof 10, that is, having a minimum value equal to or greater than 1 and amaximum value of equal to or less than 10.

In this application, the use of the singular includes the plural andplural encompasses singular, unless specifically stated otherwise. Inaddition, in this application, the use of “or” means “and/or” unlessspecifically stated otherwise, even though “and/or” may be explicitlyused in certain instances. In this application, the articles “a,” “an,”and “the” include plural referents unless expressly and unequivocallylimited to one referent.

Whereas particular embodiments of this invention have been describedabove for purposes of illustration, it will be evident to those skilledin the art that numerous variations of the details of the presentinvention may be made without departing from the invention.

1. A double-sided, polygonal cutting insert, comprising: a firstsurface; a second surface opposite the first surface; a plurality ofside surfaces extending between the first surface and the secondsurface, each side surface is perpendicular to the first surface and thesecond surface; a plurality of primary cutting edges formed at anintersection between the plurality of side surfaces and the firstsurface; and a plurality of wiper edges formed at an intersectionbetween the plurality of side surfaces and the first surface, each wiperedge having a step protruding radially outward from a respective sidesurface and formed with a substantially planar outer surface.
 2. Thecutting insert of claim 1, wherein each primary cutting edge is concavealong a central longitudinal axis of the cutting insert and a top edgeof the step of each wiper edge is convex along the central longitudinalaxis of the cutting insert.
 3. The cutting insert of claim 2, whereinthe convex wiper edge has a radius, R_(W), of from 10 to 100millimeters.
 4. The cutting insert of claim 1, wherein the plurality ofprimary cutting edges and the plurality of wiper edges are arranged inan alternating fashion.
 5. The cutting insert of claim 1, wherein eachprimary cutting edge and each adjacent wiper edge form a compound curve.6. The cutting insert of claim 1, wherein the second surface isidentical to the first surface.
 7. The cutting insert of claim 1,further comprising a plurality of corner radiuses extending between thefirst and second surfaces and each of the plurality of side surfaces. 8.The cutting insert of claim 7, wherein each of the plurality of cornerradiuses are identical to each other.
 9. The cutting insert of claim 7,wherein the plurality of corner radiuses extend between each of theplurality of primary cutting edges and each of the plurality of wiperedges.
 10. The cutting insert of claim 1, wherein a length, CL, of eachprimary cutting edge and each wiper edge is described by the followingequation:CL=IC tan(22.5)−CR, where, IC is a diameter of an inscribed circle ofthe cutting insert, and CR is equal to a magnitude of the corner radius.11. A double-sided, polygonal cutting insert, comprising: a firstsurface; a second surface opposite the first surface; a plurality ofside surfaces extending between the first surface and the secondsurface; a plurality of primary cutting edges formed at an intersectionbetween the plurality of side surfaces and the first surface, and aplurality of primary cutting edges formed at an intersection between theplurality of side surfaces and the second surface; and a plurality ofwiper edges formed at an intersection between the plurality of sidesurfaces and the first surface and a plurality of wiper edges formed atan intersection between the plurality of side surfaces and the secondsurface, each wiper edge having a step extending radially outward from arespective side surface and formed with a substantially planar outersurface.
 12. The cutting insert of claim 11, wherein each primarycutting edge is concave along a central longitudinal axis of the cuttinginsert and top edge of the step of each wiper edge is convex along thecentral longitudinal axis of the cutting insert.
 13. The cutting insertof claim 12, wherein the convex wiper edge has a radius, R_(W), of from10 to 100 millimeters.
 14. The cutting insert of claim 11, wherein theplurality of primary cutting edges and the plurality of wiper edges arearranged in an alternating fashion.
 15. The cutting insert of claim 11,wherein each primary cutting edge and each adjacent wiper edge form acompound curve.
 16. The cutting insert of claim 11, wherein the secondsurface is identical to the first surface.
 17. The cutting insert ofclaim 11, further comprising a plurality of corner radiuses extendingbetween the first and second surfaces and each of the plurality of sidesurfaces.
 18. The cutting insert of claim 17, wherein each of theplurality of corner radiuses are identical to each other.
 19. Thecutting insert of claim 11, wherein a length, CL, of each primarycutting edge and each wiper edge is described by the following equation:CL=IC tan(22.5)−CR, where, IC is a diameter of an inscribed circle ofthe cutting insert, and CR is equal to a magnitude of the corner radius.20. A cutting tool comprising a tool body having a plurality of pocketsfor mounting a cutting insert as recited in claim 1, wherein at leastone primary cutting edge of a first cutting insert mounted in a firstpocket and at least one wiper edge of a second cutting insert mounted ina second pocket contact a workpiece during a cutting operation, therebyproducing a high-quality surface finish on the workpiece.